Method and apparatus for tensioning and anchoring tensioning members

ABSTRACT

An improved method and apparatus for tensioning and anchoring tensioning members in a concrete structure and the like wherein there is provided a wedge support member having wedge-receiving pockets coaxially aligned with the anchor seats in an anchor block permitting the anchor wedges to first be inserted into the pockets and the support member then threaded over the tensioning members for supporting the anchor wedges in a released position during tensioning. The wedge support member preferably is made as an integral part of the tensioning assembly and coaxially aligned therewith so that the entire integral assembly may be threaded over the tensioning members. The tensioning assembly applies the desired tension to the tensioning members and thereafter an advancing member moves the support member to forcibly insert the anchor wedges into the respective anchor seats whereby when the tensioning assembly is released from the tensioning members the anchor wedges clampingly engage the tensioning members to anchor them under tension. Automatic release apparatus in the tensioning assembly facilitates the release of the tensioning members from the tensioning assembly by a further release or relaxation of the tensioning assembly.

United States Patent 191 Andrews METHOD AND APPARATUS FOR TENSIONING AND ANCHORING TENSIONING MEMBERS James S. Andrews, Westminster, C010.

[73] Assignee: American Stress Wire Corporation, Englewood, C010.

22 Filed: July 6,1971

21 Appl. No.: 159,959

[75 Inventor:

Primary ExaminerCh arlie T. Moon Attorney, Agent, or FirmReilly and Lewis Jan. 29, 1974 [5 7] ABSTRACT An improved method and apparatus for tensioning and anchoring tensioning members in a concrete structure and the like wherein there is provided a wedge support member having wedge-receiving pockets coaxially aligned with the anchor seats in an anchor block permitting the anchor wedges to first be inserted into the pockets and the support member then threaded over the tensioning members for supporting the anchor wedges in a released position during tensioning. The wedge support member preferably is made as an integral part of the tensioning assembly and coaxially aligned therewith so that the entire integral assembly may be threaded over the tensioning members. The tensioning assembly applies the desired tension to the tensioning members and thereafter an advancing member moves the support member to forcibly insert the anchor wedges into the respective anchor seats whereby when the tensioning assembly is released from the tensioning members the anchor wedges clampingly engage the tensioning members to anchor them under tension. Automatic release apparatus in the tensioning assembly facilitates the release of the tensioning members from the tensioning assembly by a further release or relaxation of the tensioning assembly.

15 Claims, 4 Drawing Figures METHOD AND APPARATUS FOR TENSIONING AND ANCHORING TENSIONING MEMBERS This invention relates to improvements in tensioning and anchoring a plurality of tensioning members and more particularly to an improved method and apparatus for tensioning and anchoring of a plurality of tensioning members extending through a concrete structure or the like.

l-leretofore, apparatus f tensioning and anchoring cable or wire tensioning members has been provided wherein an anchor block includes tapered wedgereceiving seats in passages through which the tensioning members extend and are arranged to receive anchoring wedges to anchor the tensioning members to the anchor block under tension provided by a separate tensioning assembly. A previous practice has been to place the anchor wedges in the wedge-receiving seats in the anchor block prior to threading the tensioning assembly over the tensioning members and outside or rearwardly of the anchor head to provide a hold-up member for limiting movement of the anchor wedges out of the wedge seats and retaining the anchor wedges in frictional engagement with the tensioning members at all times during tensioning of the stressing members, as exemplified by U. S. Pat. No. 3,412,511 to Dietrich. However, it has been found to be highly desirable to position the wedges initially out of the wedge-receiving seats in separate support member in alignment with the wedge-receiving seats during tensioning and, following tensioning, to forcibly insert the anchor wedges into the wedge seats prior to releasing the tension on the tensioning members whereby to achieve more immediate, positive anchoring.

Accordingly, it is an object of this invention to provide improved method and apparatus for tensioning a plurality of multiple strand tensioning members or tendons to anchor an anchor block through which tensioning members extend.

Another object of this invention is to provide a novel and improved method and apparatus wherein the anchor wedges are normally supported in a released position relative to the associated wedge seats while the tensioning members are being tensioned and then are positively advanced into the wedge seats independently of the tensioning assembly.

Yet another object of this invention is to provide a support for the anchor wedges which is preferably an integral part of the tensioning assembly which allows the anchor wedges to be initially inserted thereinto rather than the anchor block and to be supported independently of the anchor block so that the entire assembly may first be threaded over a plurality of tensioning members and the anchor wedges be positioned for forcible insertion into the wedge-receiving seats following the tensioning of the members.

Yet a further object of this invention is to provide an improved automatic release device for a novel separate support member for the anchor wedges separate from the anchor block which release device will automatically release the tensioning assembly from the members to be tensioned as the tensioning assembly is relaxed for ready removal from the tensioned members and anchor block.

Another object of this invention is to provide method and apparatus for anchoring tensioning members characterized by an axially movable support member with magnetic means to normally hold the anchor wedges in a released position away from the anchor block during the tensioning of the tensioning members and an actuating rod operable independently of the tensioning as- 5 sembly to positively move the anchor wedges into associated wedge seats whereby when the tensioning members are released by the tensioning assembly the anchor wedges will clampingly engage the tensioning members.

In accordance'with the present invention in a preferred embodiment shown there is provided for use with an anchor block with passages through which a plurality of multiple strand tensioning members extend, anchor wedge-receiving seats at the end of each passage and an anchor wedge adapted to be inserted into each wedge-receiving seat. A tensioning assembly including a movable ram having a stressing wedgereceiving seat formed therein adapted to It ceive stressing wedges is arranged to releasably grip and move radially inwardly to tension the tensioning members. An axially slidable support member is located forwardly of and is coaxially aligned with the ram and has pockets each with a magnet which receive and support each anchor wedge in a coaxial alignment with the wedgereceiving seats in a released position away from its respective seat during tensioning. The anchor wedges are first inserted into the pockets and the wedge support member is threaded over the tensioning members. The wedge support member shown in an integral part of the forward end of the tensioning assembly so the entire assembly is threaded over the tensioning members. By means of an actuating rod attached to the support member the anchor wedges are forcibly inserted into when the tensioning members are released from the tensioning assembly, the anchor wedges clampingly engage the tensioning members to anchor same under tension. Stationary unseating tubes are provided in the passage of the ram which extend partially into the wedge seats to automatically unseat the tensioning wedges during the return stroke or relaxation of the movable ram of the tensioning assembly to automatically release the tensioning assembly from the anchoring assembly.

Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary longitudinal sectional view of apparatus for tensioning and anchoring tensioning members embodying features of the present invention with the anchor wedges being disposed in the released position and the movable ram is disposed in the fully retracted position;

FIG. 2 is an enlarged fragmentary sectional view showing the relationship of the wedge seat and tensioning members in the released position;

FIG. 3 is a fragmentary longitudinal sectional view of a forward portion of the apparatus shown in FIG. I with the anchoring head and anchor wedges in the anchoring position; and

FIG. 4 is a fragmentary longitudinal sectional view of the forward portion of the apparatus shown in FIG. 1 with the anchoring head in the retracted position wherein the tensioning assembly may be removed from the anchor block.

their respective wedge seats after tensioning whereby Referring now to the drawings, in FIG. 1 there is shown a portion of a concrete structure or body 1 I having a plurality of elongated tensioning members 12. Each tensioning member 12 shown is made of a number of individual wires which are twisted together to form an integral member which may be referred to with reference to the drawing as a strand. A group of the strand or stranded tensioning members make up a tendon. A typical strand 12 is made of seven wires which are twisted together to make a complete turn about every 8 inches. However, it is understood that the term tensioning members as used herein is intended to refer to any type of member such as cable, stranded wire or solid structure which may be used in applying tension to a concrete structure or the like. Each strand or tensioning member 12 extends through a bearing plate 13 recessed in an outer face of the concrete body 1 l. The typical pattern or arrangement for the tensioning members is in a circumferentially spaced array with some being further displaced radially from a common center than others. The bearing plate 13 has an outer face flush with the outer face of the concrete body 11. The bearing plate 13 is provided with a suitable passage through which each strand extends.

In general, the tensioning is carried out by means of a tensioning assembly generally designated A disposed at a rear position and the anchoring is carried out by means of an anchoring assembly generally designated 8 disposed at a forward position. The terms forward and rear as used herein refer to the directions toward and away, respectively, from the outer face of the concrete body 11.

The anchoring assembly B is located immediately adjacent the bearing plate 13. Assembly B includes an anchor block 15 with a forward vertical face which abuts directly against the bearing plate 13 having passages 16 through which the tensioning members 12 extend. Each passage 16 is enlarged and tapered or diverges rearwardly to form a wedge seat 17 in a rear portion of the anchor block which is adapted to receive an anchor wedge 18. Push tubes 19, shown in a retracted position, are provided in each passage 16 to unseat the anchor wedges 18 for detensioning.

A detensioning screw 21 extends through a central passage 22 in the anchor block and terminates in a head 23 located rearwardly of the rear face of the anchor block remote from the bearing plate 13 and inside the end of the ram barrel of the tensioning assembly as described more fully hereinafter. By turning the detensioning screw 21, previously tensioned strands may be detensioned in a manner fully described in my copending application entitled METHOD & APPARATUS FOR DETENSIONING STRANDED CABLE.

The tensioning assembly A in general includes a stationary ram barrel 25 and a movable ram 26 which is coaxially aligned with and slidably movable in the ram barrel between retracted positions and extended positions. The ram barrel 25 is in the form of a hollow, generally cylindrical body having an enlarged rear end portion 27 formed with an opening in the rear end. The ram 26 is of a shape complementary to that of the barrel 25 and sized to slide through the open end thereof. As with the barrel, the ram has an elongated, hollow rear end portion 28.

The rear open end of the enlarged rear end portion of the barrel 25 is provided with internal threads 31 which receive an annular closure ring 32 having external threads and an inner surface shaped and sized to surround the enlarged rear end portion 28 of the ram and provide a rear guide surface for the reciprocal axial movement of the enlarged end portion 28 of the ram in the barrel portion 27. The forward portion of the ram telescopes or is coaxially aligned in the barrel in a close-fitting slidably movable relation to the inner surface thereof for guided, reciprocal movement therein.

The motive power for the tensioning assembly A is preferably hydraulic fluid under pressure supplied by a suitable hydraulic pressure system (not shown). A power pressure chamber is formed in a space between the ram barrel and ram and more specifically is between parallel radially extending surfaces 33 and 34 of the enlarged end portions 27 and 28, respectively. A high pressure input port 35 is provided in the ram barrel opening into the power pressure chamber 30 which will cause the ram to move rearwardly toward the extended position in the power stroke.

A return pressure chamber 37 is formed in an axially extending space between parallel surfaces of the enlarged end portions 27 and 28 rearwardly of the power pressure chamber 30. Return pressure chamber 37 is provided by reducing the diameter of the rear section of the enlarged end portion 28 of the ram to form a notch 38. A low pressure port 39 is provided in the enlarged end portion 29 of the barrel rearwardly of the high pressure port to introduce fluid under pressure into the return chamber. The pressure in the return chamber 37 moves the ram toward the retracted position in a return stroke.

Suitable seals are provided between the stationary and movable peripheral external and internal surfaces of the ram and barrel, respectively, to retain the hydraulic pressure in the respective pressure chambers. For the power chamber 30 a forward O-ring seal 41 and a rear O-ring seal 42 are provided in recesses in the barrel and ram, respectively, located forwardly and rearwardly, respectively, of the power chamber 30. Forward and rear O-ring seals 43 and 44 are provided in recesses in the ram and closure ring, respectively, of the return chamber 37. An additional O-ring end seal 45 is provided in the closure ring and a seal 46 is provided in an axial groove in the barrel against which the bottom surface of the closure ring 32 presses as it threads into the rear end of the barrel.

The ram 26 is provided with a plurality of mutually parallel passages 48 adapted to slidably receive each strand 12 when the tensioning assembly is first positioned over each strand with the forward end against the anchor block 13. The rear end portions of passages 48 are formed with enlarged rearwardly divergent surfaces which form wedge seats 49 opening into the ho]- low part of the enlarged end portion 28.

Each stressing wedge 51 encompasses a strand 12 and the forward end is in the wedge seat 49. As the ram is moved rearwardly toward the extended position in the power stroke the stressing wedges 54 are brought into engagement with the wedge seats 49 which in turn compress or contract to engage the associated strand. A further rearward movement of the ram produces a tension or stress in each strand. A retainer plate 57 with suitable passages aligned with those in the ram is provided ashort distance rearwardly of the bottom of the enlarged end portion of the ram to limit the rearward movement of the stressing wedges so tha each strand 12 may be readily inserted through the associated passage 48 and stressing wedges without displacing the wedges.

In order to automatically release the tensioning assembly A, a stationary unseating tube 52 is provided in each passage 48 which extends a short distance into the forward end portion of the associated stressing wedge seats 49. In the return stroke of the ram the stressing wedges move against the rear ends of the tubes 52 to release them from engagement with the seats and each strand. The unseating tubes 52 have an external diameter which is less than the internal diameter of passages 48 and allows the ram to slide freely therealong and the unseating tubes have an internal diameter which permits each strand 12 to slide freely therethrough. The unseating tubes 52 are provided with enlarged or headed portions 53 at their forward ends which are embedded or supported in recesses in a support wall 54 affixed to or forming a part of the barrel 25 forming a partitioning wall between the ram and support head 61 described hereafter. A retainer plate 55 is provided rearwardly of the support block to retain the headed portions 53 of the unseating tubes in place and hold them firmly against axial movement as the ram 26 is reciprocated.

An anchor wedge support member 61 is shown as being made in the form of a circular disc member 61b with circumferentially spaced axially extending hollow cylinders 61a, each cylinder having a hollow passage 61' in alignment and in communication with a cylindrical opening 25a in a front wall 25' shown as being made as an integral part of the ram barrel and coaxially aligned therewith. While it is understood that the wedge support member 61 may be made separate from the tensioning assembly in the preferred form shown it is an integral part thereof which facilitates a rapid assembly over the tensioning members and the removal therefrom as described more fully hereinafter. The openings 25a are coaxially aligned with the wedgereceiving slots 17 and tensioning members 12 of the tendon and form pockets for supporting the anchor wedges. An annular magnet 62 is mounted in a recess in the front end of each cylinder 61a to releasably hold the anchor wedges in place in the pockets. This support arrangement for the anchor wedges permits the anchor wedges to be inserted into the pockets and the support member 61 along with the tensioning assembly then to be simultaneously threaded over each strand l2, making it much easier than when the anchor wedges are inserted into the anchor block. The support wall 54 has passages 63 through which the tensioning members extend.

As best seen in FIGS. 1 and 2 the support member 61 is normally positioned as shown in FIG. 1 and the diameter thereof is sized relative to the anchor wedges so that each magnet normally holds an anchor wedge 18. A hollow push rod 64 is connected to the base portion 61b and extends axially through the hollow central passage 26' of the ram to terminate at the rear open end of the ram in an impact block 65 in the form of a nut threaded on external threads at the rear end of the push rod. The external diameter of the push rod 64 is slightly less than the internal diameter of the central passage 26' of the ram so that the ram moves freely relatively thereto. The wedge-setting support member 61 is normally in the retracted rear position during the tensioning of each strand and is movable in a forward direction to forcibly insert the anchor wedges into associated anchor wedge-receiving seats 17. This may be done by applying an impact tool such as a hammer to the impact block 65 or by manually grasping the push rod and moving it forwardly into the hollow of the ram to positively advance the support head and thereby the anchor wedges are seated in the associated anchor seats. When each strand or the tension is released by the tensioning assembly as above described, the anchor wedges clampingly engage each strand in the wedge seats to anchor each strand under tension. A partitioning wall 54 is provided between disc member 61b and the forward end of the ram which acts as a rear limit for the support member 61.

Each of the wedges 18 and 51 above-described has a hollow bore and preferably is made up of a pair of semi-cylindrical members which are capable of lateral expansion and contraction within the associated wedge seat. With the wedges in the released position shown in FIGS. 1 and 2, the central bore of the wedge is of a larger diameter than the external diameter of the strand to be out of engagement therewith and permit the strand to be passed freely therethrough or removed therefrom. However, when the wedges are moved into engaement with the associated wedge seats, the wedges move to a contracted or gripping position shown in FIGS. 3 and 4 in a clamping engagement with the associated strand. The inner surfaces of the wedges which are usually irregular or serrated to firmly grip against the strand to positively anchor the strand to the anchor block or to the ram. In regard to the anchor wedges, when each strand is released by the tensioning assembly the anchor wedges are pulled by the engagement with the strand under tension to firmly anchor each strand under tension to the anchor block.

In the full sequence for the above-described apparatus the tensioning wedges and anchor wedges are initially positioned as shown in FIGS. 1 and 2 with the anchor wedges being inserted into the pockets 25a in the support member and the entire integral assembly being threaded over the tendon. The ram receives hydraulic fluid under pressure at the high pressure port 35, pressurizing the power chamber 30 to move the ram rearwardly causing the tensioning wedges 51 to seat in the associated tensioning wedge seats 49. Continued rearward movement of the ram then applies the desired tension to each of the strands 12. The push rod 64 is then slidably moved forwardly to positively advance the anchor wedges 18 into the anchor wedge seats 17 during which time the tension is kept on each strand. The fluid is then released from the power pressure chamber 30 letting the strand 12 advance forwardly to pull the anchor wedge 18 into clamping engagement with the anchor block 15. Fluid under pressure is then introduced into the return pressure chamber 37 to relax or retract the ram. Toward the end of the return stroke the ram and the rear ends of the unseating tubes 52 engage the forward ends of the tensioning wedges and automatically cause them to unseat. Thereafter tensioning assembly A is removed from the strand and anchor block leaving the anchor wedges 18 in the anchor block to retain tension on each strand 12.

From the foregoing it is apparent that the abovedescribed method and apparatus including support pockets in a support head operatively associated with the tensioning assembly permits a positioning of the anchor wedges in structure other than the anchor block and a threading of the assembly over each strand of the multiple strand tendon. The present invention avoids close tolerances and results in a reduction in the required length of each strand and a reduction in the total number of parts required as well as many installation labor saving advantages.

It is understood that various modifications and changes in the construction and arrangement of parts and elements comprising the preferred form of the present invention may be resorted to without departing from the spirit of the present invention.

I claim: 1. In apparatus for tensioning and anchoring a plurality of tensioning members extending through wedgereceiving seats in an anchor block wherein a tensioning assembly applies a selected tension to said tensioning members and anchor wedges adapted to be seated in said wedge-receiving seats retain the tension in the tensioning members, the combination therewith comprising:

wedge support means including support portions coaxially aligned with said wedge-receiving seats and having retention means for releasably retaining the anchor wedges in spaced relation with said wedgereceiving seats during tensioning of the members by the tensioning assembly, and positive advancing means to forcibly insert the anchor wedges into the respective anchor wedge seats after tensioning whereby when the tensioning members are released from the tensioning assembly the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means. 2. In apparatus as set forth in claim 1 wherein said means for releasably retaining the anchor wedges includes magnetic means.

3. In apparatus as set forth in claim 2 wherein said magnetic means for releasably retaining the anchor wedges is in the form of annular permanent magnets with an internal diameter sized to slidably receive each associated tensioning member.

4. In apparatus for tensioning and anchoring a plurality of tensioning members extending through wedgereceiving seats in an anchor block and wherein a tensioning assembly is adapted to simultaneously apply a preselected tension to said tensioning members, the combination therewith comprising:

a wedge support member independent of the anchor block having wedge-receiving pockets adjacent and coaxially aligned with said anchor wedge seats in which a plurality of anchor wedges are initially inserted, said wedge support member including retention means for releasably retaining the anchor wedges in spaced relation with said wedgereceiving seats during tensioning by the tensioning assembly, and

advancing means for moving the wedge support member to forcibly insert the anchor wedges into the respective wedge-receiving seats after tensioning, whereby when the tensioning assembly is released from the tensioning members the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means.

5. In an improved apparatus for tensioning and anchoring tensioning members having an anchor assembly including an anchor block, a plurality of wedgereceiving seats through which the tensioning members extend, an anchor wedge adapted to anchor each tensioning member, and a tensioning assembly including a stationary housing having a ram movable therein adapted to apply a preselected tension to said members,'the improvement comprising:

wedge support means including support portions coaxially aligned with said wedge-receiving seats, and retention means to normally support a plurality of anchor wedges in a released position during tensioning of the members by the tensioning assembly, and

positive advancing means to forcibly insert the anchor wedges from the wedge support means into the respective anchor wedge seats after tensioning whereby when the tensioning members are released from the tensioning assembly the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means.

6. In apparatus as set forth in claim 5 wherein said wedge support means includes a housing portion forming a coaxial extension of the housing of the tensioning assembly to form an integral part thereof whereby said integral assembly may be conjointly threaded over the tensioning members.

7. In apparatus as set forth in claim 5 further including means in the tensioning assembly to automatically release the tensioning assembly from the tensioning members as the ram is returned to a retracted position.

8. Apparatus as set forth in claim 5 wherein said stationary housing and movable ram have hollow enlarged end portions with a power pressure chamber being formed in a space between axially extending surfaces of said enlarged end portions and a return pressure chamber being formed between axially extending surfaces of said enlarged end portions rearwardly of said power chamber.

9. Apparatus as set forth in claim 5 including means to introduce hydraulic fluid under pressure into said power chamber and said return chambers to reciprocate said ram in said barrel.

10. Apparatus as set forth in claim 5 wherein sealing means between adjacent surfaces of said ram and barrel retains the pressure in said power chamber and return chamber.

11. Apparatus for tensioning and anchoring a plurality of stranded members in a concrete structure comprising in combination:

an anchor block positioned on an outer face on the concrete structure having passages through which the strand members extend, an anchor wedgereceiving seat in a rear portion of each of said passages,

anchor wedges adapted to be releasably inserted into said anchor wedge-receiving seats,

a tensioning assembly coaxially aligned with the passages in the anchor block and mounted rearwardly thereof including a stationary barrel, a movable ram, having passages through which the strand members extend, and stressing wedges adapted to be releasably inserted into stressing wedge seats formed in the passages of the movable ram whereby an extension of the ram causes the stressing wedges to move axially into the stressing wedge seats and grip the strand members to apply an axialtension to said strand members, said tensioning assembly having release means to automatically re- 9 lease the tensioning assembly from the strand members as the ram is returned to the retracted position, and an anchor wedge support assembly coaxially aligned with and forming an integral forward extension of the tensioning assembly, said wedge support assembly including a housing portion forming a forward axial extension of said stationary barrel and a movable support member formed with pockets to normally receive the anchor wedges, retention means in said movable support member to retain said anchor wedges in a releasable position out of engagement with the anchor wedge seats during the movement of said ram, and a hollow push rod secured to said support member and extending through the central portion of the ram to which an axial force is applied to forcibly insert the anchor wedges in the associated seats whereby when the strand members are released by the tensioning assembly the anchor wedges will clampingly engage the stranded members in the wedge seats to anchor the strands to the anchor block under tension and will be released from the retension means.

12. In an improved method of tensioning and anchoring tensioning members wherein there is provided an anchoring assembly including an anchor block provided with internal anchor wedge-receiving seats and an anchor wedge on each tensioning member adapted to extend into the anchor wedge seats, the steps of:

supporting the anchor wedges in a releasable position spaced from the associated anchor wedgereceiving seats as tension is applied to the members by said tensioning assembly,

forcibly inserting the anchoring wedges into the wedge-receiving seats while said tensioning members are held under tension, and

releasing tension from the tensioning members so that the anchor wedges engage the tensioning members to anchor the tensioning members to the anchor block. 13. In a method as set forth in claim 12 wherein said anchor wedges are moved coaxially with the movement of the tensioning assembly.

14. In a method as set forth in claim 12 further including the step of automatically releasing the tension ing members as the tensioning assembly is relaxed from the tensioning members.

15. In an improved method of tensioning and anchoring a plurality of tensioning members extending through wedge-receiving seats in an anchor block wherein there is provided a tensioning assembly for simultaneously applying a preselected tension to the tensioning members, the steps of:

providing a plurality of wedge-receiving pockets coaxially aligned with the wedge-receiving seats,

releasably retaining anchor wedges in each wedgereceiving pocket in spaced relation with said wedge-receiving seats,

threading the anchor wedges over the tensioning members,

applying a preselected tension to the tensioning members,

forcibly inserting the anchor wedges into the wedgereceiving seats, and

relaxing the tension applied to the tensioning members by the tensioning assembly whereby the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and the anchor wedges are released from their retained position in the wedge-receiving pocket. 

1. In apparatus for tensioning and anchoring a plurality of tensioning members extending through wedge-receiving seats in an anchor block wherein a tensioning assembly applies a selected tension to said tensioning members and anchor wedges adapted to be seated in said wedge-receiving seats retain the tension in the tensioning members, the combination therewith comprising: wedge support means including support portions coaxially aligned with said wedge-receiving seats and having retention means for releasably retaining the anchor wedges in spaced relation with said wedge-receiving seats during tensioning of the members by the tensioning assembly, and positive advancing means to forcibly insert the anchor wedges into the respective anchor wedge seats after tensioning whereby when the tensioning members are released from the tensioning assembly the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means.
 2. In apparatus as set forth in claim 1 wherein said means for releasably retaining the anchor wedges includes magnetic means.
 3. In apParatus as set forth in claim 2 wherein said magnetic means for releasably retaining the anchor wedges is in the form of annular permanent magnets with an internal diameter sized to slidably receive each associated tensioning member.
 4. In apparatus for tensioning and anchoring a plurality of tensioning members extending through wedge-receiving seats in an anchor block and wherein a tensioning assembly is adapted to simultaneously apply a preselected tension to said tensioning members, the combination therewith comprising: a wedge support member independent of the anchor block having wedge-receiving pockets adjacent and coaxially aligned with said anchor wedge seats in which a plurality of anchor wedges are initially inserted, said wedge support member including retention means for releasably retaining the anchor wedges in spaced relation with said wedge-receiving seats during tensioning by the tensioning assembly, and advancing means for moving the wedge support member to forcibly insert the anchor wedges into the respective wedge-receiving seats after tensioning, whereby when the tensioning assembly is released from the tensioning members the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means.
 5. In an improved apparatus for tensioning and anchoring tensioning members having an anchor assembly including an anchor block, a plurality of wedge-receiving seats through which the tensioning members extend, an anchor wedge adapted to anchor each tensioning member, and a tensioning assembly including a stationary housing having a ram movable therein adapted to apply a preselected tension to said members, the improvement comprising: wedge support means including support portions coaxially aligned with said wedge-receiving seats, and retention means to normally support a plurality of anchor wedges in a released position during tensioning of the members by the tensioning assembly, and positive advancing means to forcibly insert the anchor wedges from the wedge support means into the respective anchor wedge seats after tensioning whereby when the tensioning members are released from the tensioning assembly the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and are released from the retention means.
 6. In apparatus as set forth in claim 5 wherein said wedge support means includes a housing portion forming a coaxial extension of the housing of the tensioning assembly to form an integral part thereof whereby said integral assembly may be conjointly threaded over the tensioning members.
 7. In apparatus as set forth in claim 5 further including means in the tensioning assembly to automatically release the tensioning assembly from the tensioning members as the ram is returned to a retracted position.
 8. Apparatus as set forth in claim 5 wherein said stationary housing and movable ram have hollow enlarged end portions with a power pressure chamber being formed in a space between axially extending surfaces of said enlarged end portions and a return pressure chamber being formed between axially extending surfaces of said enlarged end portions rearwardly of said power chamber.
 9. Apparatus as set forth in claim 5 including means to introduce hydraulic fluid under pressure into said power chamber and said return chambers to reciprocate said ram in said barrel.
 10. Apparatus as set forth in claim 5 wherein sealing means between adjacent surfaces of said ram and barrel retains the pressure in said power chamber and return chamber.
 11. Apparatus for tensioning and anchoring a plurality of stranded members in a concrete structure comprising in combination: an anchor block positioned on an outer face on the concrete structure having passages through which the strand members extend, an anchor wedge-receiving seat in a rear portion of each of said passages, anchor wedges adapted to be releasably iNserted into said anchor wedge-receiving seats, a tensioning assembly coaxially aligned with the passages in the anchor block and mounted rearwardly thereof including a stationary barrel, a movable ram, having passages through which the strand members extend, and stressing wedges adapted to be releasably inserted into stressing wedge seats formed in the passages of the movable ram whereby an extension of the ram causes the stressing wedges to move axially into the stressing wedge seats and grip the strand members to apply an axial tension to said strand members, said tensioning assembly having release means to automatically release the tensioning assembly from the strand members as the ram is returned to the retracted position, and an anchor wedge support assembly coaxially aligned with and forming an integral forward extension of the tensioning assembly, said wedge support assembly including a housing portion forming a forward axial extension of said stationary barrel and a movable support member formed with pockets to normally receive the anchor wedges, retention means in said movable support member to retain said anchor wedges in a releasable position out of engagement with the anchor wedge seats during the movement of said ram, and a hollow push rod secured to said support member and extending through the central portion of the ram to which an axial force is applied to forcibly insert the anchor wedges in the associated seats whereby when the strand members are released by the tensioning assembly the anchor wedges will clampingly engage the stranded members in the wedge seats to anchor the strands to the anchor block under tension and will be released from the retension means.
 12. In an improved method of tensioning and anchoring tensioning members wherein there is provided an anchoring assembly including an anchor block provided with internal anchor wedge-receiving seats and an anchor wedge on each tensioning member adapted to extend into the anchor wedge seats, the steps of: supporting the anchor wedges in a releasable position spaced from the associated anchor wedge-receiving seats as tension is applied to the members by said tensioning assembly, forcibly inserting the anchoring wedges into the wedge-receiving seats while said tensioning members are held under tension, and releasing tension from the tensioning members so that the anchor wedges engage the tensioning members to anchor the tensioning members to the anchor block.
 13. In a method as set forth in claim 12 wherein said anchor wedges are moved coaxially with the movement of the tensioning assembly.
 14. In a method as set forth in claim 12 further including the step of automatically releasing the tensioning members as the tensioning assembly is relaxed from the tensioning members.
 15. In an improved method of tensioning and anchoring a plurality of tensioning members extending through wedge-receiving seats in an anchor block wherein there is provided a tensioning assembly for simultaneously applying a preselected tension to the tensioning members, the steps of: providing a plurality of wedge-receiving pockets coaxially aligned with the wedge-receiving seats, releasably retaining anchor wedges in each wedge-receiving pocket in spaced relation with said wedge-receiving seats, threading the anchor wedges over the tensioning members, applying a preselected tension to the tensioning members, forcibly inserting the anchor wedges into the wedge-receiving seats, and relaxing the tension applied to the tensioning members by the tensioning assembly whereby the anchor wedges clampingly engage the tensioning members to anchor the tensioning members under tension and the anchor wedges are released from their retained position in the wedge-receiving pocket. 